--Russell King [off-list ref] wrote (on Tuesday, August 09, 2005 08:08:53 +0100):

On Tue, Aug 09, 2005 at 02:59:53PM +1000, Nick Piggin wrote:

quoted

That would work for swsusp, but there are other users that want to
know if a struct page is valid ram (eg. ioremap), so in that case
swsusp would not be able to mess with the flag.

The usage of "valid ram" here is confusing - that's not what PageReserved
is all about.  It's about valid RAM which is managed by method other
than the usual page counting.  Non-reserved RAM is also valid RAM, but
is managed by the kernel in the usual way.

The former is available for remap_pfn_range and ioremap, the latter is
not.

On the other hand, the validity of an apparant RAM address can only be
tested using its pfn with pfn_valid().

Can we straighten out the terminology so it's less confusing please?

pfn_valid() doesn't tell you it's RAM or not - it tells you whether you
have a backing struct page for that address. Could be an IO mapped device,
a small memory hole, whatever.

M.

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